The first large study to characterize the histopathology of extracted leads from cardiac implantable electronic devices (CIEDs) shows that microscopic venous injuries during transvenous lead extraction (TLE) are common but may not be recognized clinically.
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“This was a wake-up call,” says Cleveland Clinic electrophysiologist Khaldoun G. Tarakji, MD, MPH, principal author of the study, which was presented at the American Heart Association Scientific Sessions 2017 and published simultaneously in Heart Rhythm. “Between 1.2 and 1.4 million CIEDs are implanted each year. These devices have saved thousands of lives and improved the quality of life for many more patients. However, with this increase in CIEDs, we have been encountering more cases where these devices and leads need to be removed, whether due to infection, lead malfunction or other indications. Extraction of these leads is usually performed percutaneously using special tools, with excellent success and low clinical complication rates.”
Scope of the clinical problem
The rate of major complications from TLE is estimated to be 1 to 2 percent. Among those complications is laceration of the central veins, which often can be fatal. While the low rate of major complications is welcome, it makes it difficult to identify predictors of complications and makes risk-benefit assessment a challenge.
So Dr. Tarakji and colleagues set out to define the incidence and extent of venous injuries after TLE on a microscopic level and compare them with the incidence of clinically documented venous lacerations. They did so by microscopically reviewing tissue samples from all patients undergoing TLE of pacemaker and implantable cardioverter-defibrillator leads at Cleveland Clinic during a 30-month period from 2013 to 2016. Leads that were more than one year old or required additional tools for removal were included in the study, thereby meeting Heart Rhythm Society criteria for the definition of TLE.
In all, 861 leads were extracted from 461 patients. A variety of extraction techniques were used, based on operator preference and the clinical situation. All operators were electrophysiologists experienced in TLE. The leads and surrounding tissue were sent to the pathology laboratory, where they were fixed in formalin. Pathologic examination was standardized to allow examination of areas covered by tissue cuffs along the length of the lead.
“We believe this is the first study to characterize microscopic findings of extracted leads among a large patient cohort,” Dr. Tarakji observes.
Injuries common, major complications rare
Vein injury was defined as the presence of the intermediate layer (tunica media) or outer layer (tunica adventitia) of the venous wall around the extracted lead. The venous injury was considered transmural (see Figure for example) if the adventitial layer was present. Despite a very low rate of clinical adverse events (1 percent), vein injury was seen at a microscopic level in 80 of the 861 extracted leads (9.3 percent) among 72 out of the total 461 patients (15.6 percent). The majority of these injuries were transmural.
Figure. Transverse section of a fibrous cuff dissected from around an extracted lead with evidence of transmural venous injury. All three layers of the vein are present (between the small arrows) along with evidence of thermal injury from the use of laser-powered sheath.
Only five patients (1.1 percent) experienced major complications requiring surgical or percutaneous intervention. “Clearly, microscopic vein injuries are common with lead extraction but often not recognized clinically,” says Dr. Tarakji.
Helping to predict risk
Predictors of vein injury included older age of lead, defibrillator (vs. pacemaker) leads and the use of laser-powered sheaths.
“We observed a correlation between vein injury and older lead age,” notes Dr. Tarakji. “Injuries weren’t common with leads that were one to five years old, but they were significantly higher with both pacemaker and defibrillator leads after five years. This information can help with decision-making when clinicians weigh whether to remove or abandon a lead, especially in noninfectious indications for extraction.”
Several observations may explain the absence of significant clinical complications in patients with vein injury, Dr. Tarakji and his co-authors wrote:
- In 20 percent of extracted leads with vein injury, the injury was located at or near the pocket access site.
- In 18.8 percent of extracted leads with vein injury, the injury involved a partial wall thickness that may not have resulted in a perforation.
- A transmural vein injury detected microscopically will not always lead to perforation of the superior vena cava due to the presence of supportive tissue outside the vein proper.
How the findings could affect practice
“Venous injuries with lead extraction happen more frequently than we observe clinically, so we should be prepared,” Dr. Tarakji says. “A rate of 1 to 2 percent of clinical complications that could be life-threatening is 1 to 2 percent too many.” At Cleveland Clinic, he notes, TLE is performed by experienced electrophysiologists in a hybrid OR with backup provided by their cardiothoracic surgical colleagues.
Dr. Tarakji says these new findings can help guide further research comparing different lead designs and different extraction tools. “Clinical comparison is difficult when the incidence of clinical complications is one to two percent, because we need to study thousands of patients in order to show a difference in outcomes,” he explains. “With histopathology detecting 10 percent of leads causing vascular injury, we can reach conclusions more rapidly and efficiently.”
How to best avoid these injuries
“The best strategy is to avoid the need for TLE to begin with,” he advises. “This can be accomplished by minimizing CIED infection, improving lead designs and expanding the battery longevity of these device to minimize the need for frequent procedures.”
Cleveland Clinic is leading global clinical trials to assess new technologies to minimize CIED infections, Dr. Tarakji notes. “The technological advancements with the development of subcutaneous ICDs and leadless pacemakers are a major leap toward the future of the field of CIEDs,” he says. “In the next decade or two, endovascular leads may perhaps become obsolete.”